1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/kdebug.h>
3 #include <linux/kprobes.h>
4 #include <linux/export.h>
5 #include <linux/notifier.h>
6 #include <linux/rcupdate.h>
7 #include <linux/vmalloc.h>
8 #include <linux/reboot.h>
9
10 /*
11 * Notifier list for kernel code which wants to be called
12 * at shutdown. This is used to stop any idling DMA operations
13 * and the like.
14 */
15 BLOCKING_NOTIFIER_HEAD(reboot_notifier_list);
16
17 /*
18 * Notifier chain core routines. The exported routines below
19 * are layered on top of these, with appropriate locking added.
20 */
21
22 static int notifier_chain_register(struct notifier_block **nl,
23 struct notifier_block *n)
24 {
25 while ((*nl) != NULL) {
26 WARN_ONCE(((*nl) == n), "double register detected");
27 if (n->priority > (*nl)->priority)
28 break;
29 nl = &((*nl)->next);
30 }
31 n->next = *nl;
32 rcu_assign_pointer(*nl, n);
33 return 0;
34 }
35
36 static int notifier_chain_cond_register(struct notifier_block **nl,
37 struct notifier_block *n)
38 {
39 while ((*nl) != NULL) {
40 if ((*nl) == n)
41 return 0;
42 if (n->priority > (*nl)->priority)
43 break;
44 nl = &((*nl)->next);
45 }
46 n->next = *nl;
47 rcu_assign_pointer(*nl, n);
48 return 0;
49 }
50
51 static int notifier_chain_unregister(struct notifier_block **nl,
52 struct notifier_block *n)
53 {
54 while ((*nl) != NULL) {
55 if ((*nl) == n) {
56 rcu_assign_pointer(*nl, n->next);
57 return 0;
58 }
59 nl = &((*nl)->next);
60 }
61 return -ENOENT;
62 }
63
64 /**
65 * notifier_call_chain - Informs the registered notifiers about an event.
66 * @nl: Pointer to head of the blocking notifier chain
67 * @val: Value passed unmodified to notifier function
68 * @v: Pointer passed unmodified to notifier function
69 * @nr_to_call: Number of notifier functions to be called. Don't care
70 * value of this parameter is -1.
71 * @nr_calls: Records the number of notifications sent. Don't care
72 * value of this field is NULL.
73 * @returns: notifier_call_chain returns the value returned by the
74 * last notifier function called.
75 */
76 static int notifier_call_chain(struct notifier_block **nl,
77 unsigned long val, void *v,
78 int nr_to_call, int *nr_calls)
79 {
80 int ret = NOTIFY_DONE;
81 struct notifier_block *nb, *next_nb;
82
83 nb = rcu_dereference_raw(*nl);
84
85 while (nb && nr_to_call) {
86 next_nb = rcu_dereference_raw(nb->next);
87
88 #ifdef CONFIG_DEBUG_NOTIFIERS
89 if (unlikely(!func_ptr_is_kernel_text(nb->notifier_call))) {
90 WARN(1, "Invalid notifier called!");
91 nb = next_nb;
92 continue;
93 }
94 #endif
95 ret = nb->notifier_call(nb, val, v);
96
97 if (nr_calls)
98 (*nr_calls)++;
99
100 if (ret & NOTIFY_STOP_MASK)
101 break;
102 nb = next_nb;
103 nr_to_call--;
104 }
105 return ret;
106 }
107 NOKPROBE_SYMBOL(notifier_call_chain);
108
109 /*
110 * Atomic notifier chain routines. Registration and unregistration
111 * use a spinlock, and call_chain is synchronized by RCU (no locks).
112 */
113
114 /**
115 * atomic_notifier_chain_register - Add notifier to an atomic notifier chain
116 * @nh: Pointer to head of the atomic notifier chain
117 * @n: New entry in notifier chain
118 *
119 * Adds a notifier to an atomic notifier chain.
120 *
121 * Currently always returns zero.
122 */
123 int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
124 struct notifier_block *n)
125 {
126 unsigned long flags;
127 int ret;
128
129 spin_lock_irqsave(&nh->lock, flags);
130 ret = notifier_chain_register(&nh->head, n);
131 spin_unlock_irqrestore(&nh->lock, flags);
132 return ret;
133 }
134 EXPORT_SYMBOL_GPL(atomic_notifier_chain_register);
135
136 /**
137 * atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain
138 * @nh: Pointer to head of the atomic notifier chain
139 * @n: Entry to remove from notifier chain
140 *
141 * Removes a notifier from an atomic notifier chain.
142 *
143 * Returns zero on success or %-ENOENT on failure.
144 */
145 int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
146 struct notifier_block *n)
147 {
148 unsigned long flags;
149 int ret;
150
151 spin_lock_irqsave(&nh->lock, flags);
152 ret = notifier_chain_unregister(&nh->head, n);
153 spin_unlock_irqrestore(&nh->lock, flags);
154 synchronize_rcu();
155 return ret;
156 }
157 EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
158
159 /**
160 * __atomic_notifier_call_chain - Call functions in an atomic notifier chain
161 * @nh: Pointer to head of the atomic notifier chain
162 * @val: Value passed unmodified to notifier function
163 * @v: Pointer passed unmodified to notifier function
164 * @nr_to_call: See the comment for notifier_call_chain.
165 * @nr_calls: See the comment for notifier_call_chain.
166 *
167 * Calls each function in a notifier chain in turn. The functions
168 * run in an atomic context, so they must not block.
169 * This routine uses RCU to synchronize with changes to the chain.
170 *
171 * If the return value of the notifier can be and'ed
172 * with %NOTIFY_STOP_MASK then atomic_notifier_call_chain()
173 * will return immediately, with the return value of
174 * the notifier function which halted execution.
175 * Otherwise the return value is the return value
176 * of the last notifier function called.
177 */
178 int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
179 unsigned long val, void *v,
180 int nr_to_call, int *nr_calls)
181 {
182 int ret;
183
184 rcu_read_lock();
185 ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
186 rcu_read_unlock();
187 return ret;
188 }
189 EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
190 NOKPROBE_SYMBOL(__atomic_notifier_call_chain);
191
192 int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
193 unsigned long val, void *v)
194 {
195 return __atomic_notifier_call_chain(nh, val, v, -1, NULL);
196 }
197 EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
198 NOKPROBE_SYMBOL(atomic_notifier_call_chain);
199
200 /*
201 * Blocking notifier chain routines. All access to the chain is
202 * synchronized by an rwsem.
203 */
204
205 /**
206 * blocking_notifier_chain_register - Add notifier to a blocking notifier chain
207 * @nh: Pointer to head of the blocking notifier chain
208 * @n: New entry in notifier chain
209 *
210 * Adds a notifier to a blocking notifier chain.
211 * Must be called in process context.
212 *
213 * Currently always returns zero.
214 */
215 int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
216 struct notifier_block *n)
217 {
218 int ret;
219
220 /*
221 * This code gets used during boot-up, when task switching is
222 * not yet working and interrupts must remain disabled. At
223 * such times we must not call down_write().
224 */
225 if (unlikely(system_state == SYSTEM_BOOTING))
226 return notifier_chain_register(&nh->head, n);
227
228 down_write(&nh->rwsem);
229 ret = notifier_chain_register(&nh->head, n);
230 up_write(&nh->rwsem);
231 return ret;
232 }
233 EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
234
235 /**
236 * blocking_notifier_chain_cond_register - Cond add notifier to a blocking notifier chain
237 * @nh: Pointer to head of the blocking notifier chain
238 * @n: New entry in notifier chain
239 *
240 * Adds a notifier to a blocking notifier chain, only if not already
241 * present in the chain.
242 * Must be called in process context.
243 *
244 * Currently always returns zero.
245 */
246 int blocking_notifier_chain_cond_register(struct blocking_notifier_head *nh,
247 struct notifier_block *n)
248 {
249 int ret;
250
251 down_write(&nh->rwsem);
252 ret = notifier_chain_cond_register(&nh->head, n);
253 up_write(&nh->rwsem);
254 return ret;
255 }
256 EXPORT_SYMBOL_GPL(blocking_notifier_chain_cond_register);
257
258 /**
259 * blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
260 * @nh: Pointer to head of the blocking notifier chain
261 * @n: Entry to remove from notifier chain
262 *
263 * Removes a notifier from a blocking notifier chain.
264 * Must be called from process context.
265 *
266 * Returns zero on success or %-ENOENT on failure.
267 */
268 int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
269 struct notifier_block *n)
270 {
271 int ret;
272
273 /*
274 * This code gets used during boot-up, when task switching is
275 * not yet working and interrupts must remain disabled. At
276 * such times we must not call down_write().
277 */
278 if (unlikely(system_state == SYSTEM_BOOTING))
279 return notifier_chain_unregister(&nh->head, n);
280
281 down_write(&nh->rwsem);
282 ret = notifier_chain_unregister(&nh->head, n);
283 up_write(&nh->rwsem);
284 return ret;
285 }
286 EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
287
288 /**
289 * __blocking_notifier_call_chain - Call functions in a blocking notifier chain
290 * @nh: Pointer to head of the blocking notifier chain
291 * @val: Value passed unmodified to notifier function
292 * @v: Pointer passed unmodified to notifier function
293 * @nr_to_call: See comment for notifier_call_chain.
294 * @nr_calls: See comment for notifier_call_chain.
295 *
296 * Calls each function in a notifier chain in turn. The functions
297 * run in a process context, so they are allowed to block.
298 *
299 * If the return value of the notifier can be and'ed
300 * with %NOTIFY_STOP_MASK then blocking_notifier_call_chain()
301 * will return immediately, with the return value of
302 * the notifier function which halted execution.
303 * Otherwise the return value is the return value
304 * of the last notifier function called.
305 */
306 int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
307 unsigned long val, void *v,
308 int nr_to_call, int *nr_calls)
309 {
310 int ret = NOTIFY_DONE;
311
312 /*
313 * We check the head outside the lock, but if this access is
314 * racy then it does not matter what the result of the test
315 * is, we re-check the list after having taken the lock anyway:
316 */
317 if (rcu_access_pointer(nh->head)) {
318 down_read(&nh->rwsem);
319 ret = notifier_call_chain(&nh->head, val, v, nr_to_call,
320 nr_calls);
321 up_read(&nh->rwsem);
322 }
323 return ret;
324 }
325 EXPORT_SYMBOL_GPL(__blocking_notifier_call_chain);
326
327 int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
328 unsigned long val, void *v)
329 {
330 return __blocking_notifier_call_chain(nh, val, v, -1, NULL);
331 }
332 EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
333
334 /*
335 * Raw notifier chain routines. There is no protection;
336 * the caller must provide it. Use at your own risk!
337 */
338
339 /**
340 * raw_notifier_chain_register - Add notifier to a raw notifier chain
341 * @nh: Pointer to head of the raw notifier chain
342 * @n: New entry in notifier chain
343 *
344 * Adds a notifier to a raw notifier chain.
345 * All locking must be provided by the caller.
346 *
347 * Currently always returns zero.
348 */
349 int raw_notifier_chain_register(struct raw_notifier_head *nh,
350 struct notifier_block *n)
351 {
352 return notifier_chain_register(&nh->head, n);
353 }
354 EXPORT_SYMBOL_GPL(raw_notifier_chain_register);
355
356 /**
357 * raw_notifier_chain_unregister - Remove notifier from a raw notifier chain
358 * @nh: Pointer to head of the raw notifier chain
359 * @n: Entry to remove from notifier chain
360 *
361 * Removes a notifier from a raw notifier chain.
362 * All locking must be provided by the caller.
363 *
364 * Returns zero on success or %-ENOENT on failure.
365 */
366 int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
367 struct notifier_block *n)
368 {
369 return notifier_chain_unregister(&nh->head, n);
370 }
371 EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
372
373 /**
374 * __raw_notifier_call_chain - Call functions in a raw notifier chain
375 * @nh: Pointer to head of the raw notifier chain
376 * @val: Value passed unmodified to notifier function
377 * @v: Pointer passed unmodified to notifier function
378 * @nr_to_call: See comment for notifier_call_chain.
379 * @nr_calls: See comment for notifier_call_chain
380 *
381 * Calls each function in a notifier chain in turn. The functions
382 * run in an undefined context.
383 * All locking must be provided by the caller.
384 *
385 * If the return value of the notifier can be and'ed
386 * with %NOTIFY_STOP_MASK then raw_notifier_call_chain()
387 * will return immediately, with the return value of
388 * the notifier function which halted execution.
389 * Otherwise the return value is the return value
390 * of the last notifier function called.
391 */
392 int __raw_notifier_call_chain(struct raw_notifier_head *nh,
393 unsigned long val, void *v,
394 int nr_to_call, int *nr_calls)
395 {
396 return notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
397 }
398 EXPORT_SYMBOL_GPL(__raw_notifier_call_chain);
399
400 int raw_notifier_call_chain(struct raw_notifier_head *nh,
401 unsigned long val, void *v)
402 {
403 return __raw_notifier_call_chain(nh, val, v, -1, NULL);
404 }
405 EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
406
407 #ifdef CONFIG_SRCU
408 /*
409 * SRCU notifier chain routines. Registration and unregistration
410 * use a mutex, and call_chain is synchronized by SRCU (no locks).
411 */
412
413 /**
414 * srcu_notifier_chain_register - Add notifier to an SRCU notifier chain
415 * @nh: Pointer to head of the SRCU notifier chain
416 * @n: New entry in notifier chain
417 *
418 * Adds a notifier to an SRCU notifier chain.
419 * Must be called in process context.
420 *
421 * Currently always returns zero.
422 */
423 int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
424 struct notifier_block *n)
425 {
426 int ret;
427
428 /*
429 * This code gets used during boot-up, when task switching is
430 * not yet working and interrupts must remain disabled. At
431 * such times we must not call mutex_lock().
432 */
433 if (unlikely(system_state == SYSTEM_BOOTING))
434 return notifier_chain_register(&nh->head, n);
435
436 mutex_lock(&nh->mutex);
437 ret = notifier_chain_register(&nh->head, n);
438 mutex_unlock(&nh->mutex);
439 return ret;
440 }
441 EXPORT_SYMBOL_GPL(srcu_notifier_chain_register);
442
443 /**
444 * srcu_notifier_chain_unregister - Remove notifier from an SRCU notifier chain
445 * @nh: Pointer to head of the SRCU notifier chain
446 * @n: Entry to remove from notifier chain
447 *
448 * Removes a notifier from an SRCU notifier chain.
449 * Must be called from process context.
450 *
451 * Returns zero on success or %-ENOENT on failure.
452 */
453 int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
454 struct notifier_block *n)
455 {
456 int ret;
457
458 /*
459 * This code gets used during boot-up, when task switching is
460 * not yet working and interrupts must remain disabled. At
461 * such times we must not call mutex_lock().
462 */
463 if (unlikely(system_state == SYSTEM_BOOTING))
464 return notifier_chain_unregister(&nh->head, n);
465
466 mutex_lock(&nh->mutex);
467 ret = notifier_chain_unregister(&nh->head, n);
468 mutex_unlock(&nh->mutex);
469 synchronize_srcu(&nh->srcu);
470 return ret;
471 }
472 EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
473
474 /**
475 * __srcu_notifier_call_chain - Call functions in an SRCU notifier chain
476 * @nh: Pointer to head of the SRCU notifier chain
477 * @val: Value passed unmodified to notifier function
478 * @v: Pointer passed unmodified to notifier function
479 * @nr_to_call: See comment for notifier_call_chain.
480 * @nr_calls: See comment for notifier_call_chain
481 *
482 * Calls each function in a notifier chain in turn. The functions
483 * run in a process context, so they are allowed to block.
484 *
485 * If the return value of the notifier can be and'ed
486 * with %NOTIFY_STOP_MASK then srcu_notifier_call_chain()
487 * will return immediately, with the return value of
488 * the notifier function which halted execution.
489 * Otherwise the return value is the return value
490 * of the last notifier function called.
491 */
492 int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
493 unsigned long val, void *v,
494 int nr_to_call, int *nr_calls)
495 {
496 int ret;
497 int idx;
498
499 idx = srcu_read_lock(&nh->srcu);
500 ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
501 srcu_read_unlock(&nh->srcu, idx);
502 return ret;
503 }
504 EXPORT_SYMBOL_GPL(__srcu_notifier_call_chain);
505
506 int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
507 unsigned long val, void *v)
508 {
509 return __srcu_notifier_call_chain(nh, val, v, -1, NULL);
510 }
511 EXPORT_SYMBOL_GPL(srcu_notifier_call_chain);
512
513 /**
514 * srcu_init_notifier_head - Initialize an SRCU notifier head
515 * @nh: Pointer to head of the srcu notifier chain
516 *
517 * Unlike other sorts of notifier heads, SRCU notifier heads require
518 * dynamic initialization. Be sure to call this routine before
519 * calling any of the other SRCU notifier routines for this head.
520 *
521 * If an SRCU notifier head is deallocated, it must first be cleaned
522 * up by calling srcu_cleanup_notifier_head(). Otherwise the head's
523 * per-cpu data (used by the SRCU mechanism) will leak.
524 */
525 void srcu_init_notifier_head(struct srcu_notifier_head *nh)
526 {
527 mutex_init(&nh->mutex);
528 if (init_srcu_struct(&nh->srcu) < 0)
529 BUG();
530 nh->head = NULL;
531 }
532 EXPORT_SYMBOL_GPL(srcu_init_notifier_head);
533
534 #endif /* CONFIG_SRCU */
535
536 static ATOMIC_NOTIFIER_HEAD(die_chain);
537
538 int notrace notify_die(enum die_val val, const char *str,
539 struct pt_regs *regs, long err, int trap, int sig)
540 {
541 struct die_args args = {
542 .regs = regs,
543 .str = str,
544 .err = err,
545 .trapnr = trap,
546 .signr = sig,
547
548 };
549 RCU_LOCKDEP_WARN(!rcu_is_watching(),
550 "notify_die called but RCU thinks we're quiescent");
551 return atomic_notifier_call_chain(&die_chain, val, &args);
552 }
553 NOKPROBE_SYMBOL(notify_die);
554
555 int register_die_notifier(struct notifier_block *nb)
556 {
557 vmalloc_sync_mappings();
558 return atomic_notifier_chain_register(&die_chain, nb);
559 }
560 EXPORT_SYMBOL_GPL(register_die_notifier);
561
562 int unregister_die_notifier(struct notifier_block *nb)
563 {
564 return atomic_notifier_chain_unregister(&die_chain, nb);
565 }
566 EXPORT_SYMBOL_GPL(unregister_die_notifier);